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gh-138621: Increase test coverage for csv.DictReader and csv.Sniffer (GH-138622)

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* Increase test coverage for csv.DictReader and csv.Sniffer

Previously there were no tests for the DictReader fieldnames
setter, the case where a StopIteration was encountered when trying
to determine the fieldnames from the content or the case where
Sniffer could not find a delimiter.

* Revert whitespace change to comment

* Add a test that csv.Sniffer.has_header checks up to 20 rows

* Replace name and age with letter and offset

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

* Address review comment

---------

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
This commit is contained in:
Jan-Eric Nitschke
2025-11-12 01:32:26 +01:00
committed by GitHub
parent 0d7b48a8f5
commit 0e88be6f55
1 changed files with 31 additions and 0 deletions
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31
Lib/test/test_csv.py
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@@ -918,6 +918,14 @@ class TestDictFields(unittest.TestCase):
reader = csv.DictReader(f, fieldnames)
self.assertEqual(reader.fieldnames, fieldnames)
def test_dict_reader_set_fieldnames(self):
fieldnames = ["a", "b", "c"]
f = StringIO()
reader = csv.DictReader(f)
self.assertIsNone(reader.fieldnames)
reader.fieldnames = fieldnames
self.assertEqual(reader.fieldnames, fieldnames)
def test_dict_writer_fieldnames_rejects_iter(self):
fieldnames = ["a", "b", "c"]
f = StringIO()
@@ -933,6 +941,7 @@ class TestDictFields(unittest.TestCase):
def test_dict_reader_fieldnames_is_optional(self):
f = StringIO()
reader = csv.DictReader(f, fieldnames=None)
self.assertIsNone(reader.fieldnames)
def test_read_dict_fields(self):
with TemporaryFile("w+", encoding="utf-8") as fileobj:
@@ -1353,6 +1362,19 @@ ghijkl\0mno
ghi\0jkl
"""
sample15 = "\n\n\n"
sample16 = "abc\ndef\nghi"
sample17 = ["letter,offset"]
sample17.extend(f"{chr(ord('a') + i)},{i}" for i in range(20))
sample17.append("v,twenty_one") # 'u' was skipped
sample17 = '\n'.join(sample17)
sample18 = ["letter,offset"]
sample18.extend(f"{chr(ord('a') + i)},{i}" for i in range(21))
sample18.append("v,twenty_one") # 'u' was not skipped
sample18 = '\n'.join(sample18)
def test_issue43625(self):
sniffer = csv.Sniffer()
self.assertTrue(sniffer.has_header(self.sample12))
@@ -1374,6 +1396,11 @@ ghi\0jkl
self.assertIs(sniffer.has_header(self.sample8), False)
self.assertIs(sniffer.has_header(self.header2 + self.sample8), True)
def test_has_header_checks_20_rows(self):
sniffer = csv.Sniffer()
self.assertFalse(sniffer.has_header(self.sample17))
self.assertTrue(sniffer.has_header(self.sample18))
def test_guess_quote_and_delimiter(self):
sniffer = csv.Sniffer()
for header in (";'123;4';", "'123;4';", ";'123;4'", "'123;4'"):
@@ -1423,6 +1450,10 @@ ghi\0jkl
self.assertEqual(dialect.quotechar, "'")
dialect = sniffer.sniff(self.sample14)
self.assertEqual(dialect.delimiter, '\0')
self.assertRaisesRegex(csv.Error, "Could not determine delimiter",
sniffer.sniff, self.sample15)
self.assertRaisesRegex(csv.Error, "Could not determine delimiter",
sniffer.sniff, self.sample16)
def test_doublequote(self):
sniffer = csv.Sniffer()